The standard cruise control is a device that allows the motor of a vehicle to maintain a constant preselected vehicle speed without requiring the operator to depress the accelerator pedal. By automatically depressing the accelerator pedal to maintain a preselected velocity, cruise control eliminates the leg fatigue that can accompany sustained highway travel. This leg fatigue usually centers around the ankle and is the result of the varying amounts of accelerator pedal depression required of the motorist to maintain a fairly constant vehicle speed.
U.S. Pat. No. 4,590,909, assigned to the assignee of the present invention, discloses a known speed control device known by the trademark "Deaccelerator". That device, like conventional cruise control, eliminates the ankle fatigue often accompanying sustained travel. When operating a motor vehicle not equipped with a speed control device, motorists generally rest the heel of the foot on the floor while the rest of the foot is in full contact with the accelerator pedal. Varying amounts of accelerator pedal depression are required of the motorist to maintain a constant speed when encountering varying road gradients and changing wind conditions. The motorist must operate the accelerator pedal by foot movements pivotal at the ankle. In the invention of U.S. Pat. No. 4,590,909, the heel of the motorists foot need not rest on the floor during accelerator pedal operation. Instead, the motorist has the option of placing the foot, including the heel, on the accelerator pedal so that the accelerator pedal literally functions to support the foot. If a motorist attempted this in a vehicle not equipped with the Deaccelerator, the weight of the foot would provide a force greater than the counterforce provided by the four pound return spring of the accelerator pedal. The accelerator pedal would become almost completely depressed, and the speed of the vehicle would become far too great. If a motorist's foot is placed on the accelerator pedal of a vehicle equipped with the invention of U.S. Pat. No. 4,590,909, the weight of the motorist's foot will depress the accelerator pedal only far enough to maintain the selected velocity. As the vehicle moves uphill, the weight of the motorists foot will further depress the accelerator pedal to the new position required to maintain the selected velocity. As the vehicle moves downhill, the Deaccelerator will automatically move the accelerator pedal, with the motorist's foot upon it, toward an extended position to maintain the selected velocity. Thus, the prior invention eliminates ankle fatigue by automatically maintaining a preselected velocity, but, unlike cruise control, achieves speed control in conjunction with driver participation.
According to the invention of U.S. Pat. No. 4,590,909, the accelerator pedal resists further depression when a vehicle speed reaches a predetermined speed, such as the maximum legal speed limit. However, this accelerator pedal resistance may be overridden if the motorist depresses the accelerator pedal with sufficient force. When the accelerator pedal resistance is overridden, the vehicle will accelerate. When this occurs, increasing accelerator pedal resistance is imposed as a function of increases in vehicle speed.
Thus, the Deaccelerator provided speed control in conjunction with driver participation, and provided increased accelerator pedal resistance when the motorist attempted to override the speed control. If the motorist's foot is removed from the accelerator pedal, the return spring will tend to move the accelerator pedal upward, reducing the vehicle speed.
Many motorists do not like to use cruise control when there is any other traffic around, because there is a certain amount of planning ahead required that is not natural for them to do. Also, when not using cruise control, most motorists are accustomed to the often-rehearsed lateral movement of the foot when going from the accelerator pedal to the brake pedal. An increase in reaction time regarding the execution of a braking response may occur when a motorist is using cruise control because the typical lateral response is no longer effective and the placement of the motorists foot varies and must be determined each time a braking response is to be executed. The conventional Deaccelerator allows the driver to rest his or her foot on the accelerator pedal and travel at a preset speed, such as the speed limit, and is thus effective for use in heavy traffic situations. Also, the operator need only remove his or her foot from the accelerator pedal and, as in normal driving, the pedal return spring will begin to extend the pedal and slow the vehicle.
However, most heavy traffic situations are encountered on busy city streets which have a speed limit somewhat lower than the maximum legal speed. Because the Deaccelerator was originally designed to control vehicle speeds in a small range around the maximum legal speed, the cruise control function was of little use in most heavy traffic, lower speed situations. Similarly, the increased pedal resistance encountered in attempts to override the speed control mechanism was set to be engaged at the maximum legal speed limit. Thus, the Deaccelerator could not be used effectively as a vehicle speed limiting device in city driving.
In addition to the above-described dangers encountered when using conventional cruise control in heavy traffic, the conventional cruise control mechanism, such as that marketed under the trademark "Supercruise" by Dana Corporation, exhibits the following operating characteristics. If there is a malfunction, the driver must depress the brake pedal to disengage the cruise control. This removes battery power from the cruise control circuitry, and is supposed to disengage the cruise control. However, not all failures are circumvented when battery power is removed. For instance, a solenoid valve can become stuck. More specifically, the vacuum solenoid can fail to close. The solution to this problem is the use of another solenoid valve, which is powered directly by the brake pedal switch. This is an oversized unit, which will dump vacuum from the actuator even if the vacuum solenoid fails to close. One problem with this approach is that the brake pedal actuated solenoid valve can fail closed at any time with no indication of this failure until the vacuum solenoid fails to close as above. In such an instance, the vehicle will begin to overspeed, and pressing the brake pedal will not disengage the cruise control. The driver is expected to have the presence of mind to turn off the ignition.
Such hidden failures in conventional cruise control operation can be eliminated by adapting the Deaccelerator to incorporate the conventional cruise control function The adaptation is accomplished by replacing the force supplied by the driver's foot so that the Deaccelerator functions without driver participation, just as conventional cruise control systems.
Accordingly, it is an object of the present invention to provide a vehicle speed control system which eliminates hidden failure modes.
A further object of the invention is to provide a vehicle speed control system, as aforesaid, which can always be completely disengaged by disconnecting it from the vehicle battery.
A further object of the invention is to provide a vehicle speed control system, as aforesaid, which supplies, as an option, a device that replaces the function of the motorist's foot in the conventional Deaccelerator.
A further object of the present invention is to provide a Deaccelerator in which the cruising speed can be conveniently selected by the motorist.
A further object of the invention is to provide a Deaccelerator in which driver participation can be selectively obviated.
A further object of the invention is to provide a Deaccelerator in which a maximum limit on speed control settings can be conveniently selected by the operator.
A further object of the invention is to provide a speed maintaining device, as aforesaid, the components of which are of durable construction and easy maintenance.